1. Field of the Invention
This invention relates to oxazoline diesters, particularly to those in which the oxazoline ring is formed from tris(hydroxymethyl) aminomethane and a non-terminally unsaturated acid such as crotonic acid and in which the diester portion is derived from drying-oil fatty acids.
2. Description of the Prior Art
Oxazolines of the general formula ##STR1## are well known for use as drying oils either in monomeric form or in polymeric form, after homopolymerization or co-polymerization with dissimilar ethylenic monomers. In the above formula, R is the carboxylate-ion portion of a carboxylic acid and R.sup.1 is hydrogen, alkyl, or alkenyl. Such oxazolines and polymeric drying oils based thereon are shown, for instance, in U.S. Pat. No. 3,248,397 to Purcell.
The older methods of producing the monomeric oxazolines involved reacting an aminohydroxy compound and a carboxylic acid, and then condensing this reaction product with an aldehyde. This last step of condensing with an aldehyde was performed to yield the vinyl group in the position alpha to the ring.
Another method of producing the monomeric oxazolines with an alpha vinyl group is shown in U.S. Pat. No. 3,678,065 issued July 18, 1972 to Frump. This method involves reacting tris(hydroxymethyl) aminomethane, for example, with acrylic or methacrylic acid, yielding the vinyl group directly, without the need to condense with formaldehyde.
The oxazolines produced by these and other methods all contain a vinyl group in a position alpha to the ring. Although this alpha vinyl group imparts to the oxazoline monomer some air-dry capabilities, these would be enhanced if the unsaturation, while still alpha to the ring, were not terminal.